Formation of benzocyclobutenes from substituted oxocycloocta-2,8-diene-1,2-dicarboxylates

Abstract Substituted benzocyclobutenes were isolated from the reaction of substituted oxocycloocta-2,8-diene-1,2-dicarboxylates with DMAD which were themselves formed by the microwave assisted [2+2] cycloaddition of cyclic enaminones to dimethyl acetylenedicarboxylate. The high pressure hydrogenation of (1 E ,2 Z )-dimethyl 3-(dimethylamino)-7-oxocycloocta-2,8-diene-1,2-dicarboxylate gave oxabicyclo[3.3.1]non-3-ene-2,3-dicarboxylates, while use of low pressure hydrogenation resulted in only the carbonyl group being reduced to give the corresponding hydroxyl derivative which was proposed as an intermediate of the oxabicyclo[3.3.1]nonanes formed using high pressure hydrogenation.